A concentrated solar power system focuses the sun's energy to heat a working fluid to generate steam for use in a conventional heat engine, usually a steam turbine, to produce electricity. Typically, a parabolic cylindrical reflector, frequently referred to as a trough, focuses the solar energy on a receiver, or absorber, lying along the focal line of the reflector. Referring to FIG. 1, in an exemplary system, a number of reflectors 100 are installed in a large array 110, and provisions incorporated to track the movement of the sun in order that the sunlight impinging on each reflector may be concentrated on its receiver 120. The receivers are interconnected so that the working fluid can flow in continuous loops through the field and heat engine. See http://en.wikipedia.org/wiki/Concentrated_solar_power, image of part of the 354 MW SEGS solar complex in northern San Bernadino County, Calif.
Referring to FIG. 2, an energy collection mechanism suitable for use in the system of FIG. 1 may include a solar collector/concentrator 200 having a reflective surface 210 defining a parabolic cylindrical shaped trough 220. A supporting structure, such as a truss system, may be provided for the surface. The supporting structure may be adapted to change the pointing direction of the surface to, e.g., track the direction of the incoming solar energy and/or to provide for stowage of the trough structure. Structures 230a and 230b may be provided at each end of the trough to support the tubular receiver 250 which is located along the focal line of the trough. These structures are affixed to the trough in such a way that the trough can pivot about the top of the posts under the control of actuators 240. See U.S. Patent Publication No. 2013/0047978, incorporated herein by reference to the maximum extent permitted by applicable law.
Large parabolic reflectors, e.g., troughs, may be challenging and expensive to fabricate due to the high degree of surface accuracy necessary for high efficiency. A contributing factor is that the reflective surface preferably maintains parabolic accuracy over various operational conditions, including over the range of pointing angles and over variable wind and heat loading. A driving factor is that the structures, e. g., ribs and/or trusses, used for supporting the reflective surface and maintaining its accuracy need to be precisely engineered and manufactured. A common technique is to use water jet fabrication for these trusses, an expensive process. Alternatively these structures can be manufactured less precisely, but then many adjustments and alignments may need to be made in the field to the structure to achieve the necessary degree of accuracy.
There is a need for an inexpensive method for accurately forming, shaping, and maintaining structures for use with parabolic reflectors, as well as a need for large, accurately shaped reflective surfaces.